A new generation wireless communications system (NR) includes an operating frequency band above 6 GHz. To increase coverage when a power amplification capability is limited, a discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) waveform is used as a supplement to an OFDM waveform in an uplink of the NR. To further reduce a peak-to-average power ratio (PAPR) of the DFT-S-OFDM waveform, π/2-binary phase shift keying (π/2-BPSK) modulation and frequency domain spectral shaping (FDSS) technologies are introduced in the NR. An applicable range of π/2-BPSK modulation overlaps that of existing quadrature phase shift keying (QPSK) modulation. When a network device such as an NR base station (gNB) schedules user equipment in an overlapping area, a decision needs to be flexibly made between the two modulation schemes depending on an actual scenario. A modulation and coding scheme (MCS) table provides support for a modulation scheme used for communication between the network device and the user equipment.
Currently, there are mainly two types of MCS tables that provide a modulation scheme for communication between the network device and the user equipment. On one hand, in an MCS table of 802.11ad, a plurality of high-code-rate MCSs with π/2-BPSK are used. However, in a case of same spectral efficiency, low-code-rate QPSK generally can provide better performance. In addition, the MCS table of 802.11ad lacks coverage of some low-code-rate QPSK. On the other hand, in a cellular-based Narrowband Internet of Things (NB-IoT) MCS table, π/2-BPSK modulation is used for MCSs 0 and 1, and QPSK modulation is used for other MCSs. However, in the NR, for the two modulation schemes, a larger signal-to-noise ratio range may be covered, scenarios of different bandwidths need to be considered, and a fixed MCS configuration of the NB-IoT is difficult to satisfy an NR requirement.
Therefore, flexibly selecting a modulation scheme in the NR by the network device is a problem to be resolved urgently at present.